Developing Device, Process Cartridge and Image Forming Apparatus

A process cartridge comprising:

• a developing cartridge including:
• a casing configured to accommodate developer;
• a developing roller;
• and
• a seal member, at least portion of which is disposed between the developing roller and the casing, the seal member including a fabric member including a plurality of first fibers extending in a first direction;
• and
• a drum unit including a photosensitive drum disposed to face the developing roller, and on which the developing cartridge is configured to be removably mounted,
• wherein the drum unit further includes a heat radiation member configured to radiate heat of the seal member through the end surfaces of the plurality of first fibers of the seal member.